Weisman G A, De B K, Friedberg I, Pritchard R S, Heppel L A
J Cell Physiol. 1984 May;119(2):211-9. doi: 10.1002/jcp.1041190211.
Transformed mouse fibroblasts, such as 3T6, exhibit an increase in plasma membrane permeability to nucleotides and other normally impermeant molecules when incubated with external ATP in an alkaline medium low in divalent cations. Increased nucleotide permeability, induced by external ATP, occurs after a 3- to 5-min lag period. Prior to this event, there is a dramatic Na+ influx and K+ efflux, a significant reduction in the levels of intracellular ATP and organic phosphates, and a reduction in the plasma membrane potential. Accordingly, we postulate that these cellular responses to external ATP play a role in the efflux of nucleotides. Ouabain, a specific inhibitor of the plasma membrane (Na+,K+)-ATPase, acts together with low concentrations of external ATP to increase nucleotide permeability in 3T6 cells. This effect occurs at concentrations of ouabain and ATP which alone do not increase nucleotide permeability. In addition, ouabain and low concentrations of ATP alone have little effect on the level of intracellular ATP. This is in contrast to energy inhibitors and uncouplers which appear to enhance nucleotide permeability by lowering the intracellular ATP concentration. Ouabain alone causes a threefold increase in intracellular Na+ levels and a similar reduction in intracellular K+ levels under our experimental conditions, supporting the idea that ion fluxes are involved in the mechanism of permeabilization.
转化的小鼠成纤维细胞，如3T6细胞，在碱性二价阳离子含量低的培养基中与细胞外ATP孵育时，其质膜对核苷酸和其他通常不能透过的分子的通透性会增加。由细胞外ATP诱导的核苷酸通透性增加，在3至5分钟的延迟期后出现。在此事件之前，会有显著的Na⁺内流和K⁺外流，细胞内ATP和有机磷酸盐水平显著降低，质膜电位降低。因此，我们推测这些细胞对细胞外ATP的反应在核苷酸外流中起作用。哇巴因是质膜（Na⁺，K⁺）-ATP酶的特异性抑制剂，它与低浓度的细胞外ATP共同作用，可增加3T6细胞中的核苷酸通透性。这种效应在单独使用时不会增加核苷酸通透性的哇巴因和ATP浓度下发生。此外，单独的哇巴因和低浓度的ATP对细胞内ATP水平几乎没有影响。这与能量抑制剂和解偶联剂形成对比，后者似乎通过降低细胞内ATP浓度来增强核苷酸通透性。在我们的实验条件下，单独使用哇巴因会使细胞内Na⁺水平增加三倍，细胞内K⁺水平降低类似程度，这支持了离子通量参与通透性机制的观点。
